The mirror of the 150 year old "Leviathan" telescope at Birr Castle is being restored using innovative nickel plating technology developed by Nitec in Chesterfield, UK. The telescope, built by the Earl of Ross in 1848, required a new cost-effective version of the circular glass-ceramic mirror. Working with the Optical Science Laboratory (OSL) at University College London, Nitec have helped produce a mirror with an highly polished nickel coating, giving the "Leviathan" excellent "eyesight".
The circular aluminium based mirror (1.8 metres wide and 20 centimetres thick) was coated by engineers working at Nitec using electroless nickel plating technology. This chemical-based plating technique, catalysed by the aluminium and the nickel deposit itself, allowed the engineers to cover the mirror's surface with a 100 micrometer thick nickel coating which could be polished by OSL to the required finish. Using an electroless technique helped ensure an even deposit of the coating as variations in current density can cause un-evenness in the electrode plating of the nickel. A nickel-plated aluminium mirror was chosen in stead of the traditional glass-ceramic as it provided a cost effective and highly efficient replacement for the team restoring the telescope.
Nitec has developed the electroless plating technology for coating a range of appliances including computer components and a 19 tonne "swivel" components used in North Sea oil rigs. However, the "Leviathan" mirror demanded a greater level of handling and care than the company had ever experienced. David Brown, production director of Nitec, says, "I had overseen the plating of much bulkier and heavier items before, but never with such responsibility for a flawless surface". David Brooks, optician at OSL, says of the technique, "This has pushed back the boundaries of technology and achieved enormous cost savings".
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Notes For Editors
- This item is due to appear as "Nickel plating a monster mirror" by John Moorwood, in the May issue of Materials World, Volume 7, Issue 5, p.279
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